| Closed-loop Recycling Process Flow for Diamond Betavoltaics Yannick Verbelen1; Morgan Boardman2; Hugo Dominguez3; Robbie Mackenzie4; Tom Wallace Smith4; Suresh Kaluvan4; Chris Hutson4; Sophie Osbourne4; Ian Bickerton4; Talmon Firestone2; Neil Fox5; Tom Scott4; 1, Bristol, United Kingdom; 2ARKENLIGHT LTD, Colindale, London, United Kingdom; 3SCHOOL OF CHEMISTRY, UNIVERSITY OF BRISTOL, Bristol, United Kingdom; 4UNIVERSITY OF BRISTOL, Bristol, United Kingdom; 5BRISTOL CENTRE FOR FUNCTIONAL NANOMATERIALS, UNIVERSITY OF BRISTOL, Bristol, United Kingdom; PAPER: 244/Battery/Regular (Oral) SCHEDULED: 18:15/Mon. 28 Nov. 2022/Similan 2 ABSTRACT: The invention of <sup>14</sup>C-based solid state diamond power-cells offers unique opportunities for demonstrating a circular economy in relation to fissile energy production; and closed-loop recycling of these <sup>14</sup>C Diamond Betavoltaic Batteries (C14-DBB). The extremely long half-life of the radioisotope <sup>14</sup>C on a human time scale, 5730 ± 40 years, means that the power output of a C14-DBB is constant from any practical power engineering perspective. The durability of a diamond crystal on geological time scales is quite long and is the result of strong covalent bonds between carbon atoms. <sup>14</sup>C as a beta emitter has a maximum decay energy of 156 keV and a weighted mean energy of 49.5 keV, insufficient to break the covalent bonds and therefore preserving integrity of the crystal over the entire “discharge” period/half-life of the C14-DBB. <br />Whether as back-up cells for real-time clocks (RTC), volatile memory, infrastructural health monitoring, medical implants, or any other use case, this class of betavoltaics will outlive any foreseeable engineering application they are used in. An examination of the socio-economic, ecological, and regulatory interplay in relation to the use and life cycle of a <sup>14</sup>C-based diamond is meant to demonstrate the applicability of closed-loop circular economy as applied to the nuclear sector as a first of a kind demonstrator of how fissile energy production can operate in a closed-loop circular economy, not just as a means of producing energy with a significant waste stream, but a holistically integrated cycle. As a part of this cycle we demonstrate the utility of harvesting feedstock for radiovoltaics. In the next step we demonstrate the incentive to collect and recycle <sup>14</sup>C-based C14-DBB’s thus completing a closed-loop economic cycle wherein the derivative waste stream from fissile energy production is reutilised and recycled. Though this approach is not a panacea solution for how to deal with the end state waste from fissile energy production, it is our hope that this first demonstration will evince new investigations along similar lines to make maximum use of every part of the process thus converting the entire value chain to a wholly integrated and cyclical ‘value constellation’ relating to fissile energy production. <br />In this work, we specifically present a novel process flow to identify and recover C14-DBB’s from Waste Electrical and Electronic (WEE) appliances repurposing the <sup>14</sup>C-diamond into new C14-DBBs. The process uses machine vision to detect C14-DBBs on Printed Circuit Boards (PCB) using inspection cameras, and fiducial marks from the SMD assembly process to calculate the exact location of the C14-DBB on the PCB. It is then recovered using selective hot air de-soldering. Electrical contacts and package are removed in a nitric acid bath to expose the C14-DBB and recover it in a controlled environment. The <sup>14</sup>C-diamond is packaged inside a layer of non-active <sup>12</sup>C-diamond, so no radioactivity is exposed at any point in the recycling process. It is inspected using surface analysis techniques before new ohmic contacts are applied and an electrical check is performed using a flying probe tester. The recovered diamond is finally repackaged as a repurposed C14-DBB device, and valuable metals are recovered from the nitric acid solution for re-used after electro-filtration and purification. References: [1] A.O. Pavliuka, S.G. Kotlyarevskya, R.I. Kana et al., Fabrication and calibration of new carbon-14 reference standards using irradiated graphite from uranium-graphite reactors, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 1003, doi: 10.1016/j.nima.2021.165350, 2021.<br />[2] B. Dawson, The covalent bond in diamond, Proceedings of the Royal Society, 298(1454), doi: 10.1098/rspa.1967.0103, ISSN: 0080-4630, 1967.<br />[3] W. Sohn, D.-W. Kang, W.-S. Kim, An estimate of 14C inventory at Wolsong NPP in the Republic of Korea, Journal of Nuclear Science and Technology, 40(8), pp 604-613, 2003.<br />[4] V. Agarwal, J. Shelton, Z. Yanliang, Thermoelectric Generator Powered Wireless Sensor Node Prototype for Nuclear Applications. OSTI, doi: 10.2172/1467405, 2018.<br />[5] C. Jones, What happened to the nuclear-powered pacemaker?, British Journal of Cardiac Nursing, pp. 1-6, doi: 10.12968/bjca.2020.0126, ISSN: 2052-2207, 2021.<br />[6] Kneese, A. (1988). The Economics of Natural Resources. Population and Development Review, 14, 281-309. doi:10.2307/2808100<br />[7] K. Janeczek, A. Arazna, W. Steplewski, T. Serzysko, Traceability of printed circuit boards assemblies using embedded electronic components, IET Microwaves, Antennas & Propagation, 14(8), doi: 10.1049/iet-map.2019.0569, ISSN: 1751-8725, 2020.<br />[8] G. Burel, F. Bernard, W.J. Venema, Vision feedback for SMD placement using neural networks, Proc. 1995 Int. Conf. Robotics and Automation, doi: 10.1109/ROBOT.1995.525486, 1995. |
